Iranian Foreign Minister Manouchehr Mottaki said Monday he hoped talks with six world powers over its contentious nuclear program continued "in a positive light so as to reach a positive result for all sides."

Iran and six world powers held their first talks in more than a year, focusing mainly on Tehran's need to diffuse fears about its nuclear programs, an official said.

Delegates from Iran, the U.S., Russia, China, Britain, France and Germany met at a conference center in Geneva, with European Union foreign policy chief Catherine Ashton greeting Saeed Jalili, Iran's chief negotiator, in the foyer.

Tehran says it does not want atomic arms and its nuclear program is only designed to provide more power for its growing population. Yet as Iran builds up its capacity to make such weapons, neither Israel nor the U.S. have ruled out military action if Tehran fails to heed UN Security Council demands to freeze key nuclear programs.

About 75 percent of Monday's three-hour morning session was devoted to nuclear issues, said an official close to the talks. That was significant, because the Islamic Republic had come to the table insisting that the negotiations address Iran's nuclear program only peripherally - if at all.

Specific sensitive points included a renewed call by the world powers for an end to Tehran's program of uranium enrichment - an activity that the Islamic Republic says is not up for discussion, said the official, who asked for anonymity in exchange for discussing the confidential negotiations.

Publicly Iran continued to insist that enrichment and related programs were not on the agenda.

"We can't put them up for negotiation," Mottaki said in Athens. "When all the countries say that they recognize Iran's right to develop peaceful nuclear technology, there is no room for such questions."

Ashton and senior officials from the six powers at the talks told Iran that doubts about the peaceful nature of its nuclear program were among the sources of instability in the region, the official said.

Jalili's comments included other themes - including mentioning last week's assassination of an Iranian nuclear scientist and the wounding of an associate, the official said.

Iran says Majid Shahriar, the scientist killed in the bombing, was involved in a major project with Iran's nuclear agency. The wounded scientist, Fereidoun Abbasi, is suspected by the UN of links to secret nuclear activities. Iran has accused the West and Israel of being behind the assault.

Nations have a right to enrich uranium domestically and Iran insists it is doing so only to make fuel for an envisaged network of reactors and not to make fissile warhead material. But international concerns are strong because Tehran developed its enrichment program clandestinely and because it refuses to cooperate with an IAEA probe following up suspicions that it experimented with a nuclear weapons program - something Iran denies.

Officials described the initial meeting as encouraging as the two sides broke for lunch of duck with olives, char fillet with sage, rice pilaf and desert.

Bilateral sessions were planned for the afternoon, including a possible one between Jalili and U.S. Undersecretary of State William Burns and their delegations.

Jalili planned to come back to the other participants with a response to their presentations, one official said.

Mottaki, the Iranian foreign minister, sounded a note of optimism as the talks began.

"The success of the Geneva talks is affected by the approach the other side will show to today's realities, for the necessary flexibility to be shown in the shaping of the agenda of the negotiations," he told reporters.

But, underlining its commitment to enrichment, Iran on Sunday announced it had delivered its first domestically mined raw uranium to a processing facility.

Ali Akbar Salehi, head of the Atomic Energy Organization of Iran and the country's vice president, said Iran had for the first time delivered domestically mined raw uranium to a processing facility - allowing it to bypass UN sanctions prohibiting import of the material.

Salehi said Iran was now self-sufficient over the entire nuclear fuel cycle - from extracting uranium ore to enriching it and producing nuclear fuel.

Since Iran's clandestine enrichment program was discovered eight years ago, Iran has resisted both rewards - offers of technical and economic cooperation - and four sets of increasingly harsh UN sanctions meant to force it to freeze its enrichment program.

Israel has threatened to attack Iran, even though Israel is believed to have stockpiled more than 200 nuclear weapons and it is not a member of the Nuclear Nonproliferation Treaty.

U.S. Secretary of State Hillary Clinton has said it was up to Iran to restore trust about its nuclear intentions, urging it to come to Geneva prepared to firmly, conclusively reject the pursuit of nuclear weapons.

But for Iran, the main issues are peace, prosperity - and nuclear topics only in the context of global disarmament.

Iran has not and will not allow anybody in the talks to withdraw one iota of the rights of the Iranian nation, President Mahmoud Ahmadinejad said beforehand.